Temperature dependent shear band dynamics in a Zr-based bulk metallic glass

There is strong interest in determining the time scales involved in the shear banding process during plastic deformation of bulk metallic glasses. Knowing these time scales helps to understand shear banding in more detail, and may also answer the question of whether significant localised heating can occur in and near shear bands. In this study we investigated flow serrations, corresponding to discrete shear events, of a Zr52.2Ti5Cu17.9Ni14.6Al10 (Vit105) bulk metallic glass with respect to their stress drop and strain burst magnitude as well as their duration, as a function of temperature in the range of 60 C to -40 C. The results show that while the stress drop magnitude and the strain burst magnitude remain approximately constant with varying temperature, there is a strong temperature dependence of the shear event duration, ranging from approximately 1 ms at 60 C to 80 ms at -40 C. A calculation of the associated shear band velocities shows pronounced Arrhenius-type behaviour with an activation energy of 0.3 eV, in good agreement with recent potential energy landscape simulations. The strong temperature dependence of shear banding observed in this metallic glass is found to be analogous to the behaviour of other (non-metallic) amorphous materials.